1. Field of the Invention:
This invention relates to an improvement in rolling devices for filled cans, and particularly to a novel construction of a lifter and method for driving the same.
2. Prior Art:
Prior art lifters were of a forced drive system which is driven in synchronism with a chuck at all times, and of a free rotation system without the forced drive. In the free rotation system, a rapid rotation must be imparted to a can of a large volume filled with contents on the lifter, only by a seaming chuck during rolling, thus failing to achieve the rolling operation at high speeds. On the other hand, a forced drive system is advantageous in high speed operation but poses a disadvantage in that in the event a slip in the chuck or abnormal operation in rolling should occur for some cause, the lifter would not follow such a condition smoothly. This leads to a significant problem because a slight abnormality in the can or the like causes a great shock at a higher speed operation of rolling. A further problem is that a warm up operation at the time of start becomes necessary in order to provide smooth upward and downward movements of the lifter.